Messages in this thread | | | From | Ryota Ozaki <> | Date | Tue, 20 Dec 2011 13:43:17 +0900 | Subject | Re: [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state |
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Hi David,
I'm so sorry for my late reply.
On Mon, Dec 19, 2011 at 7:44 AM, David Rientjes <rientjes@google.com> wrote: > On Sun, 18 Dec 2011, Ryota Ozaki wrote: > >> /sys/devices/system/node/{online,possible} involve a garbage byte >> because print_nodes_state returns content size + 1. To fix the bug, >> the patch changes the use of cpuset_sprintf_cpulist to follow the >> use at other places, which is clearer and safer. >> > > It's not a garbage byte, sysdev files use a buffer created with > get_zeroed_page(), so extra byte is guaranteed to be zero since > nodelist_scnprintf() won't write to it. So the issue here is that > print_nodes_state() returns a size that is off by one according to
I see. It's certainly not a garbage but just a zero-cleared byte.
> ISO C99 although it won't cause a problem in practice. > >> This bug was introduced since v2.6.24. >> > > It's not a bug, the result of a 4-node system would be "0-3\n\0" and > returns 5 correctly. You can verify this very simply with strace.
Of course I confirmed the trailing '\0'. I'm sure it's not critical issue but it actually influences my script; I have to change from rstrip("\n") to rstrip("\n\0") in python. Yes, it's pretty trivial but enough to get rid of the extra for me :-)
Anyway the subject and the comment of my patch need to be fixed. I'll send a revised one later.
Thanks. ozaki-r -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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